XF86_SVGA does a truly terrible job of E's stippled window
thing on my ViRGE card. Haven't tried XF86_S3V (which is
buggier), but XF86_S3 does quite nicely on my spare
P100/Trio64, so it can't just be that the card or machine
are too slow.
The S3ViRGE driver doesn't currently accelerate stippled draws. I
believe that the next version of X will however.
This isn't a bug, more of a feature request.